CVE-2025-49710Public exploitNetwork attack vector

Browser crash via truncated hash-table allocation size

Published Jun 11, 2025 · Updated Jul 27, 2026

Integer overflow in Mozilla Firefox before 139.0.4 allows remote attackers to crash the browser by growing JavaScript Map or Set objects. OrderedHashTableImpl::rehash passes a size_t allocation size to a uint32_t allocator parameter, truncating the size before memcpy writes entries. Attacker-controlled JavaScript must execute and create an extremely large collection, consuming substantial resources before the write crash occurs.

CVSS severity9.8
Critical
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in Mozilla Firefox before 139.0.4 allows remote attackers to crash the browser by growing JavaScript Map or Set objects. OrderedHashTableImpl::rehash passes a size_t allocation size to a uint32_t allocator parameter, truncating the size before memcpy writes entries. Attacker-controlled JavaScript must execute and create an extremely large collection, consuming substantial resources before the write crash occurs.

The record

CVE
CVE-2025-49710
Published
Jun 11, 2025
Updated
Jul 27, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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